Bailey North American Species of Sigmodon. 115 



Sigmodon ochrognathus sp. nov. 



Type from the Chisos Mts., Texas, 8,000 feet altitude No. 110,333, 

 U. S. National Museum, Biological Survey Collection, 9 ad. Collected 

 June 13, 1901, by Vernon Bailey. Original No. 7681. 



General characters. Size small; tail long and hairy; pelage but 

 slightly hispid. 



Color. Upperparts yellowish gray, strongly tinged around ears, face 

 and rump with ochraceous; nose, orbital ring and base of tail clear, 

 bright ochraceous; belly white; feet buffy gray; tail blackish above, 

 buffy gray below. 



Skull. Similar to that of minimus but interparietal with a posterior 

 indentation, bullae narrower and basioccipital shorter and wider; 

 nasals short, wide, and truncate posteriorly. 



Measurements. Type: total length 260; tail 117; hind foot 29. Skutt 

 of type: basal length 28; nasals 11.6; zygomatic breadth 19; mastoid 

 breadth 13; alveolar length of upper molar series 5.5. 



Distribution. The transition zone top of the Chisos Mts., Texas and 

 6,700 feet altitude near Parral, Chihuahua. Four specimens examined 

 from the type locality, and one from near Parral. 



Sigmodon leucotis sp. nov. 



Type from the Valparaiso Mts., Zacatecas, Mexico, 8,700 feet altitude, 

 No 92,001, U. S. National Museum, Biological Survey Collection, 9 ad. 

 Collected December 2, 1897, by E. W. Nelson and E. A. Goldman. 

 Original No. 11,812. 



General characters. Size medium; tail short and hairy; pelage rather 

 soft; colors dull, with conspicuously light ears. 



Color. Upperparts dull brownish gray; ears whitish gray; belly 

 whitish; feet brownish gray; tail black, becoming brownish at the base 

 below. 



Skutt. Short, wide and heavily ridged along sides; interparietal 

 narrow, with a dividing suture across middle in 11 out of 13 specimens; 

 supraoccipital sloping, without trace of median ridge; nasals short, 

 narrow and notched at posterior end; audital bullae full and oval. 



Measurements. Average of 8 adult topotypes: total length 234; tail 

 91; hind foot 29.4. Skull of type: basal length 31; nasals 11.4; zygo 

 matic breadth 20.5; mastoid width 15; alveolar length of upper molar 

 series 6. 



Distribution. Known only from the type locality. Number of speci 

 mens examined 13. 



Remarks. The divided interparietal occurs in one other species from 

 Oaxaea, but as it is not entirely constant it is probably of little signifi 

 cance. 



